The field of the invention is wireless signal transmission, and specifically, antennas for reception and transmission of wireless signals.
Portable devices which rely upon wireless communication continue to proliferate. Internet access is being provided to portable organizers, for example. Devices exist to provide laptop computers with wireless Internet access through portable wireless phones. Antenna installations in devices such as laptop computers present special problems since the device interferes with signal reception and transmission.
The interference is typically caused by metal shielding that serves to reduce electromagnetic interference (EMI) introduced by the laptop into the environment. Conductive paint can serve the same function in laptop computers as metal shielding. Other portable devices use metal shielding or conductive paint for the same reason. In addition, metal is used in some portable devices to improve ruggedness of the devices.
The present invention is directed to such devices. In such a device it is desirable to have an antenna which is operable in a discreet position, i.e., one which is not extruding from the device. It is also desirable to have an antenna which can be extended away from the device to operate in conditions of weak signals, or possibly, to receive and/or transmit. Typical extendable and retractable antenna arrangements such as those used in portable phones, e.g., cellular phones, will not operate adjacent a ground plane.
The present invention is a dual mode antenna. The antenna of the invention connects in an inverted-F antenna feed when in a retracted position, and in a monopole antenna feed in an extended position. The antenna mounts adjacent a relatively large ground plane, such as a grounding shell included in a laptop computer display, for example.
A preferred embodiment antenna of the present invention includes an elongate radiator mounted in a non-conductive housing to permit retraction and extension of the elongate radiator. The housing includes electrical contact points that form an inverted-F antenna feed connection to the elongate radiator when the elongate radiator is in a retracted position. The electrical contact points form a monopole antenna feed connection to the elongate radiator when the elongate radiator is in an extended position.
In the preferred embodiment, the electrical contact points preferably include a lower contact point that connects to a lower galvanic contact near an end of the elongate radiator when the elongated radiator is retracted. The contact points also include an upper contact point that connects with a separate galvanic contact on the elongate radiator when the radiator is in the retracted position. The upper contact point connects with the lower galvanic contact when the elongate radiator is in an extended position. The upper contact point may include two separate points at which connection can be established or may define a length over which contact can be made by the lower galvanic contact such that a full extension of the elongate radiator is enabled while forming a monopole feed in the extended position.